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Oct. 17, 2007 – The Pap test is an annual ritual for millions of American women, but it may not be the best way to screen for cervical cancer.
In a head-to-head comparison study from Canada, DNA testing for human papillomavirus (HPV) was found to be far more accurate than traditional Pap smear testing for detecting precancerous lesions.
The HPV test was nearly 40% better at detecting these lesions than the Pap test.
HPV testing accurately detected precancerous lesions without generating false-negatives 94.6% of the time, compared with 55.4% of the time for the Pap test.?????????????????
The DNA test did produce more false-positive results than Pap testing, but the difference was not as great as some previous studies suggest.
The findings are published in the Oct. 18 issue of The New England Journal of Medicine.
“It is clear that the HPV test picks up more precancers than the Pap test, and I personally think it is a better test,” researcher Marie-Helene Mayrand, MD, of McGill University, tells WebMD. “But you will certainly find doctors who feel differently because more [false-positive] women are sent for invasive diagnostic procedures they don’t need.”
The Pap test is used to screen for abnormal cellular changes that may lead to cervical cancer. Annual testing is recommended because the test often misses slow-growing precancerous lesions.
Because a lesion can take a decade or more to turn into cancer, annual Pap testing usually finds precancerous lesions in time.
The HPV test is considered a useful addition to Pap testing for women over 30 who may be at high risk for cervical cancer, but the Canadian study is the first North American trial to assess its value as a stand-alone test.
The McGill researchers followed 10,154 Canadian women between the ages of 30 and 69 who were enrolled in the study between 2002 and 2005.
Over the course of the trial, HPV testing accurately detected pre-cancerous lesions without generating false-negatives 94.6% of the time.
Like Mayrand, study co-author Eduardo Franco, DrPH, says the superiority of the HPV test for identifying lesions without false-negatives argues in favor of its use as a standalone test
“A false-positive may be very disturbing and psychologically distressing for the patient, but in the end, she’s free of disease,” Franco notes in a news release. “False-negatives are very serious business, however. The patient will be assured that she is negative, all the while a pre-cancer has a chance to become a cancer or her existing cancer has a chance to grow.”
Mayrand says the next step is improving the HPV test’s specificity, or ability to detect pre-cancerous lesions without false-positives.
“We are working on strategies to increase the specificity of HPV testing,” she says. “This is not the last study on the subject. I think that within a few years we will find ways to make HPV testing more specific.”
Though experts disagree on the better test, the underlying message is clear: Get tested.
"The most important message remains unchanged: Women should be screened using one of three options: a conventional Pap test, liquid Pap, or Pap plus HPV test," says Debbie Saslow, PhD, director of breast and gynecologic cancer at the American Cancer Society. "For women who have access to HPV testing (e.g. insured women whose plan covers the test), the HPV test offers added benefits over [Pap tests] alone."